The administration of estrogen to female mice during a critical period in early infancy results in permanent estrogen-independent vaginal epithelial hyperplasia and a high incidence or precancerous changes in the adult animal. Vaginal carcinoma may occur in human females born to women treated with diethylstilbestrol (a synthetic estrogen) in early pregnancy. Several lines of investigation show that there may be a significant role for cyclic 3'-5' adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in controlling rates of cell replication. The hypothesis of this proposal is that steroid hormones when given at critical periods in development may directly or indirectly permanently alter tissue cyclic nucleotide metabolism, with changes in rates of epithelial proliferation and possible production of precancerous lesions; further, that the sequence of events may be interrupted by changing cyclic nucleotide levels during the critical period in the newborn animal. We propose to investigate cAMP, cGMP, and adenyl cyclase activity in vaginas from adult neonatally-treated and control animals, and on tissue from animals in whom cyclic nucleotide levels have been altered by pharmacological means. The relationship of tissue cyclic nucleotides and DNA synthesis will be studied, and we will search for distinctive species of protein and RNA in the treated and control vaginas, using specific radioisotope labeling and polyacrylamide gel electrophoresis. Developmental curves of cyclic nucleotide levels and adenyl cyclase activity in vaginas from normal newborn mice and those undergoing estrogen treatment will be established. Simultaneously, the tissue and intracellular locations of cAMP will be followed during development using immunofluorescent techniques; finally, the studies in newborn animals will be repeated as cyclic nucleotide levels are altered by drug treatment. These studies may provide insight into fundamental mechanisms of production of hormone-independent hyperplasia and potential premalignancy following neonatal steroid exposure.